FR3098051A1 - Housing for rotating electrical machine including a plastic bearing - Google Patents

Abstract

The present invention provides a casing for a rotary electrical machine comprising a first bearing and a second bearing, at least the first bearing being made of plastic, said first bearing comprising a transverse wall and a skirt extending from the transverse wall between an end connected to the transverse wall and a free end, the casing also comprising a first cooling chamber, said first cooling chamber being housed at least partially in the skirt of the first bearing. Figure for the abstract: Figure 1

Description

Casing for a rotating electric machine comprising a plastic bearing

The invention relates in particular to a rotating electrical machine comprising a casing comprising at least one plastic bearing.

The invention finds a particularly advantageous application in the field of rotating electrical machines such as alternators, alternator-starters or even reversible machines or electric motors. It is recalled that a reversible machine is a rotating electric machine capable of working reversibly, on the one hand, as an electric generator in alternator function and, on the other hand, as an electric motor, for example to start the heat engine of the motor vehicle. .

A rotating electrical machine comprises a mobile rotor in rotation around an axis and a fixed stator surrounding the rotor. In alternator mode, when the rotor is rotating, it induces a magnetic field in the stator which transforms it into electric current in order to supply the electrical consumers of the vehicle and recharge the battery. In motor mode, the stator is electrically powered and induces a magnetic field driving the rotor in rotation. The rotating electrical machine also comprises an electronic assembly comprising several power modules making it possible to rectify the current supplied by the stator. This electronic module is mounted on the casing of the machine and in particular on one of the bearings forming the casing. In addition, the casing makes it possible to maintain and protect the assembly formed by the stator and the rotor.

During the operation of the rotating electrical machine, whatever its mode of operation, certain parts heat up and can be damaged if they are not cooled. These include the stator, as well as the electronic assembly.

A cooling circuit in which a cooling fluid advantageously circulates must in particular be provided at the bearings of the casing in order to cool the machine. Such a cooling circuit advantageously comprises at least one cooling chamber, for example formed by two walls extending axially around the axis of the machine and each belonging to a different bearing, and between which is placed at least one seal ensuring the sealing of the chamber as described in the document FR3057414.

Such electric machines are heavy, in particular due to the metal casing, so the overall mass of the vehicle will increase. This increase in mass will therefore lead to an increase in fuel consumption, resulting in an increase in pollution.

According to the invention, the casing for a rotating electric machine comprises a first bearing and a second bearing, at least the first bearing being made of plastic, the said first bearing comprising a transverse wall and a skirt extending from the transverse wall between an end connected to the transverse wall and a free end, the casing also comprising a first cooling chamber, said first cooling chamber being housed at least in part in the skirt of the first bearing.

Thanks to the invention, the bearing obtained is lighter and less expensive, manufacturing being simplified. In addition, the cooling chamber being made of plastic, that is to say non-porous, we limit the problems of leakage. It also avoids the problems of corrosion, and fouling of the cooling fluid.

According to other characteristics taken individually or in combination:

the skirt of the first bearing comprises a double wall, the first cooling chamber being housed in the double wall of the skirt;

the casing comprises at least one seal arranged between the bearings to seal the first cooling chamber;

the first bearing comprises at least one radial reinforcement element, molded into the skirt of the bearing;

the skirt of the first stage comprises an opening provided with a sleeve adapted to allow the transfer of fluid between the first cooling chamber and the exterior to the first chamber;

at least a portion of the plastic forming the skirt of the first bearing is filled with fillers suitable for increasing the thermal conductivity of said portion of plastic;

the double wall of the skirt of the first bearing comprises an inner wall and an outer wall, the transverse wall of the second bearing resting on the free axial end of the skirt of the first bearing, the first cooling chamber being delimited by the walls interior and exterior of the skirt of the first bearing and by the transverse wall of the second bearing;

the second bearing also comprises a skirt extending from a transverse wall between an end connected to the transverse wall and a free end, the skirt of the second bearing also comprising a double wall, said double wall comprising an inner wall and an outer wall, the first cooling chamber being delimited by the two inner walls joined along their respective free ends and by the two outer walls joined along their respective free ends;

the casing comprises a second cooling chamber, said second chamber being hollowed out in the transverse wall of the second bearing.

The invention also relates to an X-axis rotating electric machine comprising a rotor that can rotate around the X axis, a fixed stator surrounding the rotor comprising a body, and such a casing.

It is understood by the term double wall that it is a first annular wall and a second annular wall connected by at least one of their respective axial ends.

The invention will be better understood on reading the following description and on examining the accompanying figures. These figures are given only by way of illustration but in no way limit the invention.

There is a view in longitudinal section of a rotating electric machine comprising a casing with a first cooling chamber according to a first embodiment of the present invention;

There is a part of the longitudinal sectional view of the machine in the first embodiment;

There is a view in longitudinal section of the rotating electric machine comprising a casing with a first cooling chamber according to a second embodiment of the present invention;

There is a perspective view of the rotating electrical machine illustrating a second crankcase cooling chamber;

Identical, similar or analogous elements retain the same references from one figure to another. It will also be noted that the various figures are not necessarily on the same scale.

The embodiments which are described below are in no way limiting; it is possible in particular to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art. In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination from a technical point of view. In such a case, mention would be made in the present description.

In the rest of the description, the axial, radial, exterior and interior denominations refer to the X axis passing through the shaft 13 at its center. The axial direction corresponds to the X axis while the radial orientations correspond to planes concurrent, and in particular perpendicular, to the X axis. For the radial directions, the external or internal denominations are assessed with respect to the same X axis, the internal denomination corresponding to an element oriented towards the axis, or closer to the axis. axis with respect to a second element, the external denomination designating a distance from the axis. Furthermore, the denominations upper and lower as well as above/below or even front/rear refer to the pulley. Thus an upper or top or front face being a face oriented in the direction of the pulley while a lower or bottom or rear face being a face oriented in the opposite direction of the pulley.

FIG. 1 represents a compact and polyphase rotary electric machine 10, in particular for a motor vehicle. This rotating electrical machine 10 transforms mechanical energy into electrical energy, in alternator mode, and can operate in motor mode to transform electrical energy into mechanical energy. This rotating electrical machine 10 is, for example, an alternator, an alternator-starter, a reversible machine or an electric motor.

The rotating electric machine 10 comprises a casing 11. Inside this casing 11, it further comprises a shaft 13 mounted in rotation with respect to the casing around the axis X, a rotor 12 integral in rotation with the shaft 13 and a stator 15 surrounding the rotor 12. The rotational movement of the rotor 12 therefore takes place around an axis X.

A splined end of the shaft 13 ensures the mechanical connection of the electric machine with an external element to transmit the rotational movement to the shaft 13 or to the shaft 13 to transmit its rotational movement.

The rotor 12 has a body in the form of a stack of laminations. Permanent magnets are implanted in body cavities. The stator 15 comprises a body in the form of a stack of laminations provided with notches, equipped with insulator of notches for the mounting of a connected electrical winding. The winding is electrically connected to an electronic control module 24.

The housing 11 comprises assembled a first bearing which will be in the following description the front bearing 16, and a second bearing, which will be in the following description the rear bearing 17. At least one of the two bearings is made of plastic.

The bearings 16, 17 are hollow in shape and are obtained for example by molding. The bearing may in particular be made of thermoplastic. As a variant, the bearing could be made of thermo-hard.

A cooling circuit is provided to cool the machine. The cooling circuit, allowing the flow of a cooling fluid inside the machine 10. In this case, the cooling fluid is a water-based fluid possibly containing antifreeze. As a variant, the cooling fluid may be oil-based.

The cooling circuit advantageously comprises a first cooling chamber 49, delimited by the front and rear bearings, which makes it possible to circulate the fluid around the assembly of the stator 15 and the rotor 12 to cool the machine.

In a first embodiment illustrated in Figure 1, the front bearing 16 comprises a transverse wall 45 provided in its center with the housing for receiving the rear bearing 18 and delimiting an opening for the passage of the shaft 13. The front bearing 16 further comprises a skirt 47 projecting from an outer periphery of the transverse wall 45. The skirt has an annular shape of axial orientation extending towards the rear bearing 17. The rear bearing 17 also comprises a transverse wall 48 provided in its center with the housing for receiving the rear bearing 19. The front and rear bearings are secured to one another so as to form the casing containing the machine.

The rear bearing 17 has for example only a transverse wall 48 without extension in the form of a skirt. The front bearing skirt 47 covers the stator 15 over its entire height and the rear bearing 17 is a cover without a skirt, the front and rear bearings have no covering surface around the X axis.

The skirt of the front bearing 47 comprises a double wall, that is to say that the skirt of the front bearing is formed of two radially concentric annular walls around the axis X, a radially inner wall 47a and a radially outer wall 47b, as illustrated in Figure 2. The radially inner wall 47a is positioned facing the winding and the radially outer wall 47b is positioned facing the outside. Each wall 47a, 47b extends along the X axis in annular form between an end connected to the transverse wall of the bearing 45 and a free opposite end. The two walls 47a, 47b of the double wall are therefore interconnected at the level of the transverse wall of the bearing 45. The free ends of the inner and outer walls are the ends not connected to each other and not connected to the transverse wall.

In an axial section view, the skirt of the front bearing 47 therefore has a U-shape, one of the branches of the U being closer to the machine and one of the branches of the U being farther from the machine. Such a form of bearing is in particular easily obtained by molding.

The first cooling chamber 49 is then housed in the skirt 47 of the front bearing, between the two walls of the skirt of the front bearing 47a, 47b. The transverse wall 48 of the rear bearing 17 bears at the level of a peripheral zone on the free end of the skirt of the front bearing 16, opposite to the transverse wall of the front bearing 45. The cooling fluid circulates between the two walls 47a, 47b from the bearing skirt. More precisely, the cooling chamber 49 is delimited by the inner and outer walls, and by the peripheral zone portion of the transverse wall of the rear bearing 48.

As illustrated in FIG. 2, each free end of each wall of the front bearing 47a, 47b advantageously has a groove 470a, 470b respectively, adapted to house an O-ring 51 therein. In the peripheral zone of the transverse wall of the rear bearing 48, said transverse wall 48 in particular bears against the O-rings arranged in the previously mentioned grooves sealing the cooling chamber. More specifically, the first cooling chamber 49 comprises two O-rings 51, arranged respectively in each of the two grooves present at the level of the free ends of the inner 47a and outer 47b walls. The first cooling chamber 49 thus formed extends so as to surround the stator 15, over approximately 360 degrees, thus having an annular shape.

The fixing of the bearings 16, 17 between them to form the first chamber 49 can be carried out by means of fixing members, such as screws, passing through perforated ears projecting radially from the skirt of the bearing and intended to cooperate with tapped holes corresponding arranged in ears protruding radially from the lid.

In a similar manner, it may in particular be envisaged that the rear bearing comprises a double wall and carries the first cooling chamber and that the front bearing is in the form of a cover (not shown).

As a variant of this first embodiment, the rear bearing 17 comprises a skirt 50 projecting from an outer periphery of the transverse wall 48. The skirt of the first bearing 47 has a height along the axis X greater than or equal to the height of the body of the stator along the X axis, and the skirt of the second bearing 50 has a height along the X axis much lower than the height along the X axis of the skirt of the first bearing 47, typically at fifth of the height of the skirt of the first landing 47.

In a second embodiment illustrated in FIG. 3, the front 16 and rear 17 bearings respectively comprise a transverse wall 45, 48 and a skirt 47, 50 projecting from an outer periphery of the transverse wall 45 , 48. Each skirt 47, 50 has an annular shape of axial orientation. The skirts 47, 50 are directed axially towards each other and are secured to each other so as to form the casing containing the machine.

The skirts of the front 47 and rear 50 bearings each comprise a double wall, as described in the first embodiment. The skirt of the rear bearing 50 therefore also comprises two radially concentric walls around the axis X, inner and outer 50a, 50b. The inner and outer walls of the double wall 50a, 50b are interconnected at the transverse wall 48. The free ends of the inner 50a and outer 50b walls are the ends not connected to each other and not connected to the transverse wall 48.

The skirts of the front and rear bearings 47 and 50 are assembled at their free ends, with no overlap between the skirts. In particular, advantageously, the two inner walls 47a, 50a are assembled along their respective free ends, just as the two outer walls 47b, 50b are assembled along their respective free ends. The cooling fluid circulates in the closed annular volume thus delimited by said four walls forming the first cooling chamber, surrounding the stator over 360°. Seals are in particular provided at the junction between the double walls 47a, 50a as well as 'between the walls 47b, 50b so as to seal the chamber.

As illustrated in FIG. 3, each free end of each wall of the front bearing 47a, 47b and each free end of each wall of the rear bearing 50a, 50b advantageously has a groove 470a, 470b, 500a, 500b, respectively, adapted to accommodate an O-ring so as to seal the junction between the walls 47a, 50a and between the walls 47b, 50b.

As a variant, the cooling circuit comprises a second chamber 52 allowing the fluid to circulate at the level of the electronic control module 24.

The electrical control module 24 advantageously comprises a heat sink 240 ensuring its cooling on which are fixed in particular power modules making it possible to ensure control of the rotating electrical machine 10 in motor mode or in alternator mode. The electrical control module 24 is mounted flat, via the heat sink 240, against the rear face of the transverse wall 45 of the rear bearing 17.

The second chamber makes it possible to circulate the fluid at the level of the electronic control module 24 and the dissipator 240 in order to evacuate the calories generated by the electrical control module 24.

In a first embodiment, illustrated in Figure 4, the second chamber 52 is hollowed out in the transverse wall 48 of the rear bearing. The second chamber 52 is therefore delimited by the transverse wall of the rear bearing 17, and an axial end face of the heat sink (not visible in FIG. 4), in this case the front face. The chamber is also delimited by a gasket 520 tightly mounted between the rear bearing 17 and the heat sink. This seal thus forms a side wall of the chamber.

To this end, as illustrated by FIG. 4, the gasket which has a closed contour defining that of the chamber may be of the toric type. The seal defines an elongated C-shaped closed volume whose ends are very close together, so that the chamber extends circumferentially for more than 300 degrees and almost 360 degrees to ensure cooling of the entire surface of the heat sink 240.

As can be seen in Figure 4, a groove receiving the seal is made in the transverse wall 48. The seal can be held in the groove during assembly operations to facilitate the production of the electrical machine.

In this first embodiment, the heat sink 240 may be hollowed out in the surface delimited by the seal to increase the volume of the chamber. In other words, the volume hollowed out in the element is delimited by the groove for receiving the gasket. The use of the joint means that only one piece has to be hollowed out, which facilitates the construction of the chamber. Alternatively, only the rear bearing 17 is dug.

Preferably, the second cooling chamber 52 is arranged to allow the cooling of capacitors and/or power modules of the electrical control module. To this end, the second cooling chamber 52 passes below these elements. In other words, there is an at least partial overlap in axial projection along the X axis between the projected surface of these components and the projected surface of the second cooling chamber 52.

The dissipator 240 may advantageously comprise fins at the level of the front axial end face of the dissipator facing the rear bearing. Such fins (not visible in FIG. 4) allow in particular improved cooling of the electronic control module 24, by increasing the exchange surface. In particular in the case where the second cooling chamber 52 is hollowed out in the transverse wall of the bearing 48, the fins advantageously bathe in the cooling fluid so as to optimize the cooling.

In a second embodiment not illustrated, the second chamber 52 is integrated into the heat sink 240, that is to say that the second chamber 52 can be made during molding or machining of said heat sink 240 to define a hollow volume inside it. The second chamber 52 is thus delimited by internal faces of the dissipator 240.

The two chambers 49, 52 are interconnected by an intermediate channel (not shown) allowing the circulation of the cooling fluid between the two chambers. This intermediate channel is materialized by a fluid conduit connecting an opening in the wall of the second chamber and an opening in the wall of the first chamber.

The fluid advantageously circulates first in the second chamber 52 to cool the electronics then around the stator. Thus the second chamber 52 comprises an inlet connected to the inlet of the cooling circuit and an outlet connected to the intermediate channel. The first chamber 49 comprises an inlet connected to the intermediate channel then an outlet connected to the outlet of the cooling circuit. The fluid which enters the second chamber 52 via the inlet of the second chamber circulates in said chamber before being transferred to the first chamber 49 and then evacuated via the outlet of the first chamber.

More precisely, as illustrated in FIG. 2, an opening in the outer wall 47b of the skirt of the first bearing 47 to which is connected a sleeve 472, for example made of stainless steel, for example molded, forms an inlet connected to the intermediate channel. As a variant, the sleeve will be fitted or glued. A flexible tube may in particular be held by a plastic or metal collar at the level of the sleeve to allow the entry or exit of fluid.

A self-regulating valve may in particular be provided at the level of the coolant inlet sleeve from the second chamber to the first chamber, to adapt the pressure of the cooling fluid arriving in the first chamber according to the temperature of the fluid having already cooled electronics. To optimize heat exchange between the stator and the cooling fluid, the inner wall of the skirt 47a, 50a close to the stator will advantageously be loaded, at least locally, with fillers increasing the thermal conductivity of the plastic. A portion of the inner wall of the skirt 47a separating the liquid contained in the chamber 49 and the stator 15 will for example be loaded. As a variant, an insert, for example metal, is molded into said inner wall of the skirt of the bearing 47a, 50a to improve heat exchange. More specifically, the insert forms a portion of the wall facing the stator package, said insert being molded at its contour in the plastic bearing. The inner wall of the skirt 47a, 50a therefore comprises a metal portion and a plastic portion.

Furthermore, a radial reinforcement element 473, for example metallic, is advantageously molded into the skirt of the front bearing 47, so as to avoid the problems of thermal expansion of the front bearing, for example. The radial reinforcement element prevents deformation of the bearing skirt under radial stresses.

Claims (10)

Casing for a rotating electrical machine comprising a first bearing (16) and a second bearing (17), at least the first bearing (16) being made of plastic, the said first bearing (16) comprising a transverse wall (45) and a skirt (47 ) extending from the transverse wall between an end linked to the transverse wall and a free end,
the housing also comprising a first cooling chamber (49),
said first cooling chamber (49) being housed at least partly in the skirt of the first bearing (47). Casing according to Claim 1, in which the skirt of the first bearing (47) comprises a double wall, the first cooling chamber (49) being housed in the double wall of the skirt. Casing according to any one of the preceding claims comprising at least one seal arranged between the bearings (16, 17) to seal the first cooling chamber (49). Housing according to any one of the preceding claims, in which the first bearing (16) comprises at least one radial reinforcement element (473), molded into the skirt of the bearing (47). Housing according to any one of the preceding claims, in which the skirt of the first bearing (47) comprises an opening fitted with a sleeve (472) adapted to allow the transfer of fluid between the first cooling chamber (49) and the outside to the first chamber (49). Casing according to any one of the preceding claims, in which at least a portion of the plastic forming the skirt of the first bearing (47) is loaded with fillers suitable for increasing the thermal conductivity of the said portion of plastic. Housing according to claim 2 alone or in combination with any one of claims 3 to 6 in which:
the double wall of the skirt of the first bearing (47) comprises an inner wall (47a) and an outer wall (47b),
the transverse wall of the second bearing (48) rests on the free axial end of the skirt of the first bearing (47),
the first cooling chamber (49) being delimited by the inner (47a) and outer (47b) walls of the skirt of the first bearing and by the transverse wall (48) of the second bearing. Housing according to Claim 2 alone or in combination with any one of Claims 3 to 6, in which the second bearing (17) also comprises a skirt (50) extending from a transverse wall (48) between an end linked to the transverse wall and a free end, the skirt of the second bearing (50) also comprising a double wall,
said double wall comprising an inner wall (50a) and an outer wall (50b),
the double wall of the skirt of the first bearing (47) comprising an inner wall (47a) and an outer wall (47b),
the first cooling chamber (49) being delimited by the two inner walls (47a, 50a) joined along their respective free ends and by the two outer walls (47b, 50b) joined along their respective free ends. Housing according to any one of the preceding claims comprising a second cooling chamber (52), said second chamber being hollowed out in a transverse wall (48) of the second bearing (17). X-axis rotating electric machine including:
a rotor (12) rotatable about the X axis,
a fixed stator (15) surrounding the rotor comprising a body,
and a housing according to any preceding claim.